Before You Start A War, You Better Know What You're Fighting For
by SereneCalamity
Summary: Jace was starting to loose sight of the reason why he was fighting. Clace. OneShot.


_So this song is inspired by a line in_ Angel With A Shotgun _by The Cab. Amazing,_ amazing _song. And this plotline is inspired by_ Supernatural, _which is quickly becoming one of my favourite TV shows of all time. Haha._

 _Disclaimer: I do not own the characters, or the title, and barely the plot. Only the mistakes, which I'm sure there's a lot of , because I'm fucking exhausted._

Jace Herondale took in a deep breath as he shifted on the cheap motel bed, trying to stretch out his legs but then his feet just ended up hanging over the edge of the mattress. He let out a grunt under his breath and rolled over, trying to make himself comfortable. Opposite him, his partners things were on the ground, but he wasn't there. Sebastian Verlac was doing his usual thing that he did after they had finished a hunt; going to get drunk at some dive bar and take some girl back to her place for the night. Or, if he wasn't patient enough to do that, he would just take her to the dingy bathroom in the back of the bar. Jace wasn't into that sort of thing, though, and he hadn't been for a long time.

Honestly, he was just tired.

He was tired and he just wanted a nights sleep in a nice bed that was _actually_ long enough for him to fit and with blankets that weren't all scratchy and cheap and in a room that didn't smell as though someone had died in it.

And if there was someone there that he didn't absolutely hate to talk to and spend sometime with who he had could actually discuss what he really did all day long, that wouldn't be such a bad thing either.

But no, instead he was stuck with a fucking asshole who thought the sun shone out of his ass and really didn't think of any on except himself. The only reason the two of them stuck together was because...Well, it was because they really didn't have any one else. And in the shadow hunting game, it was suicide not to have a partner. It didn't necessarily mean that he trusted Sebastian with his life, but he trusted that Sebastian was a good fighter. Which was all he could really ask for when he had no one else.

Jace let out a huff and tried to plump up the flat, motel pillow and forced his eyes closed, trying to quiet his head.

* * *

Jace and Sebastian had met Alec Lightwood and his siblings a couple of times before, a few years ago. Alec and his sister, Isabelle Lightwood, and their little brother, Max Lightwood, were shadow hunters as well, but they weren't like Jace and Sebastian. They didn't specifically go out looking for trouble; they had mechanics garage attached to a bar that they ran and they just protected themselves as trouble came. They were a good family, and Jace had liked them, and could see himself being happy with them and trusting them, but his life wasn't just about taking trouble as it came his wife.

He felt an obligation to follow up any leads that he got, to try and protect mundanes from the things that they didn't understand. He wasn't one hundred percent certain if Sebastian felt that obligation, but that was the life that he had been born into, and he was satisfied with it.

They were facing an army of vampires that had almost got the better of them, before Alec, Izzy and a red head had burst through the doorway and come to their rescue. Jace had faltered in surprise, but then the red head had shouted at him to get his head in the game as she sent a dagger flying over his shoulder to plunge into the heart of a vampire that was bearing down on him. Jace snapped out of it, fighting with the red head at his side until they were able to get out of the nest they had stumbled in on.

Jace and Sebastian had followed the Lightwoods and their friend back to their house, and had been greeted by a disgruntled teenaged Max, arms crossed over his chest as he met them in the doorway.

A fight broke out between the Lightwoods, something about how Alec and Isabelle had promised to take Max out the next time they went out to fight. Isabelle was growling him, saying that it was a school night, and that he should be in bed, and that they had only said he could come if it wouldn't interfere with his studies.

The whole argument was so bizarrely _absurd_ for families in their line of work, that Jace couldn't stop himself from laughing out loud as he watched the three siblings. Alec had glared over at him and Isabelle had hissed that if he even thought about vocalizing support for Max, their hospitality was over. The red head had quickly said that this was a family conversation, and dragged both Sebastian and Jace from the room, taking them into the kitchen.

"Are you guys hungry?" She asked as she walked over to the fridge and looked inside.

"Uh, no, we're fine—" Jace began to say, not wanting to put her out and wanting to find out more about the arrangement in the hallway.

"Starving," Sebastian announced with a grin, making himself at home at the kitchen table and blatantly checking her out. The red head didn't seem to notice, which Jace was glad about, and he tried to be conspicuous as he shook his head at his partner.

"We've got left over pizza, if you want?"

"Sounds perfect," Sebastian flashed another smile, which also went unnoticed by the girl, who still hadn't even looked back at them. Jace sat down at the table with Sebastian, looking a little smug at the put out expression on Sebastians face. The girl pulled it out of the fridge and piled it onto a plate and put it on a microwave before leaning back against the bench and looking over at the two of them. "Anyway, I'm Seb—"

"I know who you are," she interrupted and Jace almost let out a laugh and how Sebastian snapped his jaw shut. He really wasn't used to woman like this, seemingly immune to his charms.

It only made her oh so much more attractive.

"You're Sebastian, and you're Jace," she nodded over at Jace, and her face softened a little, clearly sensing that he wasn't as big a douche as his partner was. "And you're cousins."

"And who are you?" Sebastian's tone was a little clipped.

"I'm Clary—Clarissa," she told them. "Clarissa Morgenstern." Both boys at the table went silent, their eyes wide and their eyebrows raised as they looked at her. Clary made a 'hurmph' noise at the back of her throat, not enjoying their reaction too much as the microwave beeped, indicating that it had finished. She turned around and opened it, pulling out the plate and then putting it on the table between them. "I'm just going to go and check on them," she muttered as she walked out of the room and back into the hallway. Sebastian and Jace both looked at each other over the table as they reached for a slice of pizza each.

"Morgenstern?" Jace questioned.

"As in Valentine and Jocelyn Morgenstern, you reckon?" Sebastian asked as he took a mouthful of pizza.

"I don't know any other Morgenstern's," Jace mumbled. The Morgensterns were legends among the Shadowhunter community; Valentine and Jocelyn were ruthless and effective, and somewhere along the way, they had ended up with two kids. The kids didn't slow them down, they were still hunting, and apparently both of their children were just as good as them.

Which he could now testify to since he had seen her in action.

Isabelle, Alec and Clary came back into the kitchen a few minutes later, Max noticeably absent. Isabelle sat down at the kitchen table with the two other boys and picked up a piece of pizza, biting into it and letting out a sigh. Alec walked over to the fridge and got out a beer, while Clary just leaned against the door, crossing her arms over her chest.

"It's been a while," Jace said by way of breaking the silence. "It's good to see you."

"It's good to see you too," Isabelle gave him a tight, tired smile, which quickly dropped when she looked over at Sebastian. It wasn't unusual—if girls weren't tripping over their feet to get his attention, they hated him. Isabelle was the kind of girl that could see right through any front that Sebastian put up, which meant she was in the fifty percent that couldn't stand his shit. "You know we have this nest under control," Isabelle said bluntly, cutting right to the chase. "You two don't need to be here."

"We could always work together," Jace suggested, trying to keep things calm.

"If you really had it under control, then they should all be dead and burning by now," Sebastian grunted.

"Maybe they would have been if we didn't need to deviate from our plan to save your asses," Clary snapped.

"We didn't need saving," Sebastian argued.

"Oh, don't even try to run that shit with us," Clary snorted derisively. "You were very clearly loosing that battle."

"We were _not_ —"

"Okay!" Alec raised his voice, glaring at all of them. "My brother has a Physics exam tomorrow, and he should have already been asleep hours ago." Jace's eyebrows almost disappeared into his hairline and he shook his head in disbelief. It was such a _normal_ family, completely different from the upbringing that Jace had gone through, and also every other Shadowhunter he had ever met. "Look, can we all head up to bed? We've got a spare room with a couch and a bed, so you guys can crash there, and then we'll talk about it in the morning."

"Oh, we've got a room at a motel room," Jace began.

"Don't be idiots," Isabelle muttered. "The motels around here are disgusting. You guys can crash here."

And that was how Jace ended up staying with the Lightwoods and Clary.

A week went by, and Jace and Sebastian were still there. They had sought out the vampires nest and killed the ones who were there. There were a few that had escaped, but the Shadowhunters were certain that they wouldn't be coming back anytime soon. It hadn't been an easy fight, though, and so the two boys had decided that they would take a bit of a breather, and Alec told them that they were more than welcome to stay. Sebastian was restless after a few days, but after Jace made it clear that he was intent to stay a little longer, he grumbled under his breath but didn't make any moves to clear out.

It made him realize exactly _what_ it was that he was missing.

Alec, Isabelle and Max were clearly a family. They were this almost completely normal American family that ate every night at the dinner table and took turns washing and drying the dishes and discussed their days and fought over the TV remote. Of course, the fact that there were weapons hidden around the house proved they weren't _quite_ the normal family, but it still made Jace wonder if that was something he would be able to have one day.

Because he didn't want to give up Shadowhunting—it was his life. It was all he had known. It was who he was—it was burned into his bones.

But then he wanted his fight to mean something.

He wanted someone to share it with.

That sick feeling he got when he was too late, and someone innocent died.

That relieved but not quite happy feeling when they defeated an other-wordly creature.

It needed to be someone who understood how he felt, so it needed to be someone who was already in this life—and he didn't mean Sebastian, who didn't really seem to feel _anything_ , and certainly wasn't about sharing the way he felt. He was more the kind of person who buried any sort of emotion in booze and women. And while that had worked for some time for Jace, he was now twenty-five and he wanted more than that.

In fact, he now knew what he wanted.

He wanted Clary.

Because she could be a part of this family, with the Lightwoods, and she cared about them and she felt for them, but she also wasn't satisfied with just sitting around and leading this normal life. She wanted to be out there and fighting, but she wanted to be out there and fighting with someone who was like her.

Like him.

It made sense.

Two weeks later, Clary left with them.

For almost a month, it was the three of them. They fought together, and they were effective. Sebastian hit on Clary constantly, and she turned him down, _constantly_ , and Jace just kept his distance, in that regard. He made sure he didn't make a move, because he didn't want her to feel as though she was expected to get with one of them. Sebastian went back to doing what he usually did, sleeping around, and that was when Clary and Jace became closer. She made him laugh, and she understood when he needed to talk after they hunted. They would sit in cheap hotel rooms, on the seedy, ugly coloured couches, and share a couple of beers and talk. Sometimes they fell asleep on the couch together, and there was no explaining the feeling that Jace got when he woke up with Clary curled on his chest.

He didn't need to sneak out.

He wasn't pretending to be someone he wasn't.

He knew exactly who _she_ was.

After a month of them together, they ran into another Shadowhunter, Lilith Eden. She was a few years older than them, almost thirty, and she was scarily similar to Sebastian. The two of them hit it of straight away, and the next morning, the two of them were covered in bruises and hickeys and both Jace and Clary looked thoroughly disgusted. When they fought together for the first time, it was clear that Lilith and Sebastian fought the same way; to inflict as much damage before delivering the final blow.

Two days later, the pair of them were gone when Jace and Clary woke up.

For someone that he had been travelling with years, Jace knew he should probably be a little more upset that his partner had taken off. But all he felt was relieved.

And with him out of the way, Jace and Clary were able to operate the way they both wanted.

Eventually, they stopped getting a room with two single beds, and just got one with a double mattress. And even though sometimes they would go days and days without sleep, because they were chasing down a creature, they would sleep well once they fell together. And when they were too late...Too late to save someone, to save _everyone_ , they would break together. When she began to loose faith, he would rub his fingers through her hair and he would whisper in her ear, repeating all the good that they had done. When he lost sight of their mission to protect, she would wind her body around his and pepper kisses over his face, breathing that she was never leaving him.

It was everything that Jace had ever needed.

It reminded him of everything that he was fighting for.

 _Let me know if you guys like it!_

 _Reviews make me so happy :) x_


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